Asthma can be difficult to diagnose because the symptoms are sometimes similar to other lung conditions. Initially, your doctor will ask about your symptoms and medical history. A physical exam will be done.

In addition, the following tests may be performed:

Chest X-ray

Chest x-ray is the initial imaging test for most people with symptoms of asthma. A chest x-ray can reveal other causes of wheezing (other than asthma) or complications (such as pneumonia ).

Pulmonary Function Tests (PFTs)

Pulmonary function tests (PFTs) is an instrument known as a spirometer is used to measure how much air is inhaled and expelled as you breathe. This test will measure both the amount and rate of air that can pass through your airways. The diagnosis of asthma is usually made when reversible lung airway obstruction is demonstrated on PFTs. A peak flow meter is used to measure the rate at which you expel air. Peak flow meters can also be used at home to assess the degree of airway obstruction, indicating an imminent asthma attack.

Provocation Test

People with asthma will experience a mild constriction of the airways when the drug methacholine is inhaled. If asthma is suspected, but there are no obvious symptoms of airflow obstruction on PFTs, methacholine is administered and the tests are run again. Alternative provocation tests include administration of histamine or inhalation of cold air. The diagnosis of asthma is usually made if the PFTs indicate lung airway obstruction during a provocation tests.

Allergy Tests

You may have Allergy tests if allergic asthma is suspected. A tiny allergen particle is placed under the skin with a needle. In 80% of cases, an allergic response is confirmed if the skin becomes raised or red within 20 minutes.

Peak Flow Meter

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